Successful controlled adhesion remains a desirable goal in many applications. A success in controlled adhesion might be defined as a technology that is controllable, reliable, safe, and robust enough to provide high mechanical pressure between objects. In some cases, it may be required to provide this mechanical pressure on a sufficient range of ordinary and every day materials. Such ordinary materials can ideally include those having wet, dusty, highly sloped and/or slippery surfaces. Traditional controlled adhesion technologies, such as chemical adhesives and suction cups, suffer from various drawbacks, including permanency, damage to or residue left at the applied surface, leaks, and a limited effectiveness on wet, dusty or irregular surfaces, among others.
The recent use of electroadhesive forces or electrostatic clamping as an alternative in controlled adhesion applications has proven to be advantageous on several levels. Such electroadhesive forces can be adapted to provide controlled adhesion on an electrically controllable basis without leaving residues or damaging surfaces. They can be fast acting in both on and off states, repeatable and strong, thus allowing repeatable modulation of material properties. Furthermore, a wider variety of dusty, slippery or irregular surfaces can be used with electroadhesive forces without detracting from a useful controlled adhesion outcome.
The use of electrostatic forces can also have drawbacks, however, such as limited amounts of adhesion force, the need to apply constant power to maintain adhesion, as well as a tendency toward low peel forces at the perimeter of an electroadhesive clamp that is adhered to a foreign object. Further, any need to be able to hold a load in an electrode power-off condition for a length of time, and also any need to conform to surfaces having high degree of roughness can pose to be problematic in many electroadhesive and electrostatic applications. In these and other electroadhesive applications, the types of electrodes and/or interacting surfaces can play significant roles in the strength, reliability and ready reversability of adherence between separate objects.
Other current approaches to non-permanent and/or reversible attachment of an object to a substrate that do not damage or alter the substrate include relying on van der Waals forces. These forces, which are exploited by natural geckos and more recent “artificial gecko” systems often require the use of a mechanical smoothing (pressure) force when applied to a substrate in order to induce the intimate contact, and as such these systems are typically not well suited to sustain high loads for long periods of time. Other, traditional means of fastening an object to a substrate include such means as nails or screws or adhesives (including tapes), the use of which have the disadvantages of being more permanent and potentially damaging to the substrate.
Although various materials and tools for electrostatic and electroadhesive applications have generally worked well in the past, there is always a desire for improvement. In particular, what is desired are materials and tools for such applications that allow for stronger, more reliable and/or readily reversible adherence between separate objects, without overly demanding requirements with respect to increased voltages, power demands, safety concerns and other electrical details.